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BELL SYSTEM TECHNICAL JOURNAL 



the limited resources of military field conditions. This type of interstage 

 has been employed quite widely in radar equipments designed during World 

 War II. To achieve the maximum gain per stage it is necessary to restrict 

 the total shunt capacitance of the interstage circuit to the unavoidable ele- 

 ments due to tube and circuit arrangement. Additional capacitance con- 

 tributions are avoided by the use of a variable inductance element adjustable 

 through the use of movable magnetic cores to resonate the network to the 

 desired midband IF value. The shunt resistance element is chosen to 

 achieve the desired band width. 



SYNCHRONOUS 

 SINGLE TUNED 



STAGGERED 

 SINGLE TUNED 



DOUBLE 

 TUNED 



Fig. 27. — Typical IF Amplifier Interstage Circuits. Simplified schematics. 



The band width required of each individual interstage circuit of a multi- 

 stage amplifier of this type to meet an over-all band width requirement of 

 B cycles is given by 



B = AF\/2^"^ - 1 



where AF represents the band width of the indivichial interstage network, 

 defined as the band over which the response is within 3 db of the midband 

 IF value, and N is the number of interstage circuits employed. As the 

 individual interstage band width is increased to achieve the desired over-all 

 value, the gain per stage is reduced and a greater number of stages is required 



